Photochemically stabilized thio-diarylamine parasiticidal composition



Patented July 19, 1938 UNITED STATES PATENT OFFICE PHOTOCHEMICALLY STABILIZED THIO-DI- ARYLAMINE PARASITICIDAL COMPOSI TION poration of Delaware No Drawing. Application January 6, 1936, Serial No. 57,781

Claims.

The present invention relates to parasiticidal compositions which contain as an active toxic ingredient a thio-diarylamine and a substance which acts as a photochemical inhibitor to pre- 5 vent inactivation of the thio-diarylamine when exposed to sun and daylight or other lights rich in ultra-violet rays.

Thio-diarylamine compositions are being used to combat various parasiticidal pests on vege- 1 tation and have particularly been found eflicient as stomach poisons for insects. They suffer, however, from the disadvantage of being sensitive to light and oxygen, and on exposure to atmospheric conditions they gradually lose their 13 potency and become biologically inactive.

I found that ultra-violet rays greatly accelerate the atmospheric inactivation of thio-diarylamine parasiticides and I found that this inactivation can be greatly inhibited if substances are inti- 30 mately admixed with the thio-diarylamines which preferentially absorb, or otherwise prevent transmittal of ultra-violet rays, so-called ultra-violet opacifiers.

The atmospheric inactivation of thio-diarylamine parasiticides is accompanied with a discoloration which throws the color of the product toward the short wave length end of the spectrum: the original slightly yellowish to brownish thio-diarylamine becomes greenish to bluish 30 on exposure to ultra-violet light and such dis- 1 colored products greatly lose their efficiency as parasiticides.

This photochemical discoloration of thio-diarylamines can easily be shown in the case of thio-diphenylamine in the following manner:v

Strips of cloth were impregnated with a solution of thio-diphenylamine in acetone, and the solvent allowed to evaporate. These strips were exposed at about inches distance to light 40 of a mercury vapor lamp and the changes in color noted. The unexposed strips were yellow; after 3 hours they became light green, after 6 hours green, and after hours very dark green." Samples of thio-diphenylamine which through exposure to light had become dark green had a greatly diminished toxicity towards insects. The effect of ultra-violet opacifiers on the colorstability of thio-diarylamines can be tested in a similar manner by impregnating similar strips of 50 cloth with a thio-diphenylamine solution which contains in solution or suspension, for instance, 5% (based on the thio-diphenylamine content of the solution) of the susbtance to be tested.

Various substances tested in this manner have shown that after 20 hours exposure to the strong ultra-violet light substantially no green coloration appeared, though in some instances the yellowish color of the test strip turned darker.

Thio-diarylamines admixed with such opacifiers maintained substantially their full parasiticidal efficiency after exposure to sun or daylight.

Substances which have the property of absorbing or preventing the transmittal of ultra violet rays and which were found to inhibit photochemical inactivation of thio-diarylamine parasiticides are, for instance: tetramethyl diamino benzophenone (Michlers ketone), cerium compounds, for instance cerium oxide or cerium oxalate, or double salts of cerium and alkali metal salts, other rare earth metal salts, beta-methyl umbelliferon, carbon black, TiOz, etc.

The thio-diarylamine insecticides which are amenable to the effect of my novel inactivation inhibitors are water insoluble compounds of the general formula:

or from phenyl-beta-naphthylamine,

di-alpha-naphthylamine. di-beta-naphthylamine, di-biphenylamine, N,N-diphenyl-p-phenylenediamine, N,N-di-alpha naphthyl-para-phenylene-dlamine,

Nj,N-di-biph'enyl-metaphenylene-d.iamine, N,N-di-phenyl-metaphenylene-diamine, p,p'-di(phenyl-amino) di-phenylamine, etc.

The thio'derivatives obtained from these d1- arylamines are all characterised by containing the heterocyclic nucleus:

n I l N\ 1 V in which R and R are aromatic nuclei in each 01' which two adjacent carbon atoms take part in forming the heterocyclic carbon-nitrogen-sultur ring.

Some of the hydrogen atoms normally attached to R and R may be substituted, or replaced by alkyl, cycloalkyl, aryl, heterocyclic nuclei, or halogen, nitro, amino, alkoxy or aryloxy groups. I

The eflect oi the ultra-violet opaciflers, of inhibiting the photochemical inactivation of thioarylamine parasiticidal compositions is made use of by intimately mixing these substances in small amounts, for instance, of from 1 to 10%'with the parasiticidal compositions. I can for instance grind together the thio-diarylamine and the opacifler; or I may dissolve both in a common solvent and after evaporation or the solvent obtain an intimate mixture of the two. In other instances I might add the opacifler, for instance carbon black, to the molten thio-diarylamine, possibly during the process of its manufacture or in any other convenient manner. When using aqueous sprays I may dissolve the opacifler in the aqueous spray liquid or suspend it in the spray mixture.

The benefit of reduced photochemical inactivation by means of ultra-violet opacifler is available in all conventional parasiticidal compositions containing a thio-diarylamine, namely, in

aqueous sprays containing spreaders, sticking and wetting agents, etc., as well as in dry dusts which may contain the usual inert diluents such as talc, silica, etc.

In the case of thio-diphenyiamine I found that tetramethyl-diaminobenzophenone in amount of about 5% is of particular efllciency as it maintains its parasiticidal ei'iiciency on exposure totion of thio-diarylamine.

2. A parasiticidal composition stabilized against photochemical inactivation comprising thio-diphenylamine and an ultra-violet opacifler in such an amount as to retard atmospheric inactivation oi! thio-diphenylamine.

3. A parasiticidal composition comprising thio-diphenylamine and an amount of tetramethyl diamino benzophenone suflicient to stabilize the thio-diphenylamine against photochemical inactivation.

4. A parasiticidal composition comprising thio-diphenylamine and an amount of cerium oxalate suilicient to stabilize the thio-diphenylamine against photochemical inactivation.

5. A parasiticidal composition comprising thio-diphenyilamine'and an amount of betamethyi umbelliferon sumcient to stabilize the thio-diphenylamine against photochemical inactivation.

EUCLID W. BOUSQUE'I. 

